1. Field of the Invention
The present invention relates generally to an image processing apparatus, and more particularly to an image processing apparatus for recording and reproducing a synthesis image formed by superimposing, on part of image data supplied from the outside, attribute data which is also supplied from the outside and associated with the image data.
2. Description of the Related Art
This type of apparatus is widely used in the field of techniques relating to medical imaging or diagnosis. For example, in many cases, an angiogram obtained by a digital fluorography (DF) apparatus used as a diagnosing X-ray apparatus is displayed on a display device such as a TV monitor, and simultaneously a cardiogram spanning a time period from a predetermined time point to the time point of the display of the present angiogram is displayed. The view field of the X-ray fluoroscopic image is regularly circular, since the view field of the output optical image of an image intensifier tube is circular. Since the corners of the screen showing the angiogram are non-effective areas, the cardiogram may be superimposed anywhere in the corners without preventing the display of the angiogram. Thus, the synthesis image containing both the cardiogram (attribute data) and angiogram (image data) can be displayed. The angiogram obtained by the DF apparatus can be displayed in real time; however, the cardiogram cannot. The cardiogram indicates an output (cardio-potential) from an electrocardiograph over a time period between a time point at which the present angiogram is produced and a time point preceding this time point by several seconds. Thus, the output (attribute data) of the electrocardiograph is stored in a buffer memory, and a portion of the cardio-potential data corresponding to a time period associated with the angiogram obtained by the DF apparatus is read out from the buffer memory and superimposed on the angiogram. Thereby, a cardiogram is produced.
A conventional method of recording image data and attribute data relating to the above-described synthesis image will now be described. Image data from the DF apparatus are supplied to the display device and also to a recording device such as a digital VCR (video cassette recorder) and recorded successively on a video tape at every frame (more exactly, at every field). In this case, the output from the electrocardiograph has not yet been supplied to the VCR and is stored in the buffer memory. After a single diagnosing operation is completed and recording of all images is completed, all cardio-potential data associated with the single diagnosing operation are read out from the buffer memory and recorded, as a unit, next to the image data recording area of the tape. In the case of reproduction, similarly, all angiogram image data associated with the single diagnosing operation are reproduced and stored in the image memory. Thereafter, all cardio-potential data are reproduced and stored in the buffer memory. Then, the angiogram is read out from the image memory and the .cardio-potential data, which spans a time period from a time point at which the angiogram is produced to a time point preceding this time point by several seconds, are read out. The cardiogram formed on the basis of the read-out data is superimposed on a corner of the angiogram.
In the prior art described above, the image data and cardio-potential data are recorded at different places on a video tape at different time points. Thus, a time is wasted in recording the cardio-potential data, after the image data has been recorded. Despite the fact that both angiogram and cardio-potential data are simultaneously produced, these cannot be recorded simultaneously. In addition, in the case of reproduction, it is necessary to read out all angiogram data at first and then read out cardio-potential data, in order to form a synthesis image in which the cardiogram is superimposed on the angiogram. That is, the synthesis image cannot be reproduced and displayed immediately. All image data and all cardio-potential data must be reproduced even if only one synthesis image needs to be reproduced. Thus, the efficiency of the operation of the apparatus is not good.